This bus route throughout most of Central Rome is a north/south rout along the Tiber. The north route (pink line) is on the right/east bank of the Tiber until it crosses at Ponte Umberto and heads norht along Piazza Cavour on the West side of the Tiber. This route returns southward (maroon/purple line) along the left/west bank of the Tiber
In southern Rome at Via Marmorata it leaves the river and passes near the Piramide Metro Stop before heading inot a loopm and ending at Piazza dei Partigiani just east of Piramide Metro stop.
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so you could use this route if you were staying in Testaccio to get near to Centro Storico/ Piazza Navona area.